Found 8 talks width keyword astrosiesmology
Understanding stellar structure and evolution significantly impacts our understanding of the tight-knit evolution of galaxies and exoplanet systems. However, hidden behind the luminous layers of the stellar atmosphere, the deep interior of a star is eluding from direct measurements. The seismic study of waves propagating the deep interior provides the only way to measure the internal structure, dynamics, and mixing in any given star and compare it to theoretical models.
With the photometric data from space missions, such as the NASA Kepler telescope, a golden age has begun for seismology. In particular, the seismic studies of thousands of solar-like have led to numerous breakthroughs in our understanding of the stellar structure of red-giant stars. Complimentary information on stellar binarity, tidal forces, rotation, and lithium abundance provide additional constraints to characterize the advanced evolution of stars further and provide high-resolution insights into complex internal adjustments. Approaching a sample of ~1000 identified solar-like oscillators in binary systems, provided by the ESA Gaia and NASA TESS missions draws an exciting picture on the interaction of stellar and orbital evolution.
ID de reunión: 892 7515 0368
Código de acceso: 101169
Since the second half of last century, stellar evolution theory has allowed to
understand the Color Magnitude Diagram of galactic star clusters, so that now
we can explain the distribution of stars in the observed CMDs in terms of the nuclear
evolution of stellar structures and, thus, in terms of cluster age and chemical composition.
In the last decades, however, the impressive amount of data collected by photometric, astrometric,
spectroscopic and asteroseismic surveys is providing a detailed observational framework which
provides at the same time a stringent test and a challenge for the accuracy of the models.
In the same time, these stellar models are a crucial input for asteroseismology as well
as Galactic archeology studies. In this talk, we discuss (some of) the main uncertainties affecting stellar models and
how they critically impact on our capability to reliably unveil the chrono-chemo-dynamical
structure of the Galaxy.
The seminar will take place in the Aula.
Meeting ID: 843 0439 9987
Time-domain space missions have revolutionized our understanding of stellar physics and stellar populations. Virtually all evolved stars can be detected as oscillators in missions such as Kepler, K2, TESS and PLATO. Asteroseismology, or the study of stellar oscillations, can be combined with spectroscopy to infer masses, radii and ages for very large samples of stars. This asteroseismic data can also be used to train machine learning tools to infer ages for even larger stellar population studies, sampling a large fraction of the volume of the Milky Way galaxy. In this talk I demonstrate that asteroseismic radii are in excellent agreement with those inferred using Gaia and spectroscopic data; this demonstrates that the current asteroseismic data is precise and accurate at the 1-2% level. Major new catalogs for Kepler and K2 data are nearing completion, and I present initial results from both. We find unexpected age patterns in stars though to be chemically old, illustrating the power of age information for Galactic archeology. Prospects for future progress in the TESS era will also be discussed.
More than 40 years ago, Skumanich (1972) showed how rotation and magnetic activity decreased with the age of a solar-like star. While this result was based on the study of young cluster stars, later observations of other clusters, still younger than the Sun, agreed with this “gyrochronology” relationship.
With the high-quality photometric data collected by the Kepler mission, we have the opportunity to test and study the evolution of stellar dynamics to older field stars. While for clusters, the determination of stellar ages is eased by the fact that the stars were born from the same molecular cloud, it gets trickier and less precise for field stars. This is where asteroseismology plays an important role by providing more precise ages than any other classical methods.
In this talk I will mostly focus on asteroseismic targets from solar-like stars to red giants where we could measure surface rotation, core rotation, and magnetic activity. I will show how the photometric data of Kepler is providing key information in the understanding of angular momentum transport in stars and of magnetic activity at different evolutionary stages of a star like the Sun.
The Kepler spacecraft is providing photometric time series with micromagnitude precision for thousands of variable stars. The continuous time-series of unprecedented timespan open up the opportunity to study the pulsational variability in much more detail than was previously possible from the ground. We present a first general characterization of the variability of A-F type stars as observed in the Kepler light curves of a sample of 750 candidate variable A-F type stars, and investigate the relation between gamma Doradus, delta Scuti, and hybrid stars. Our results suggest a revision of the current observational instability strips, and imply an investigation of pulsation mechanisms to drive hybrid pulsations.
At the end of 2008, on ideas of teams from the Observatoire de la Côte d’Azur (OCA) and IAC, the CoRoT satellite observed the star HD 46375, known to host a non-transiting Saturn-mass exoplanet with a 3.023 day period. HD 46375 is the brightest star with a known close-in planet in the CoRoT accessible field of view. As such, it was targeted by the CoRoT additional program and observed in a CCD normally dedicated to the asteroseismology program, to obtain an ultra-precise photometric lightcurve and detect or place upper limits on the brightness of the planet. In addition, a ground-based support was simultaneously performed with the high-resolution NARVAL spectro-polarimeter to constrain the stellar atmospheric and magnetic properties. In this seminar, I will present the main results, in particular the stellar constrain we obtained thanks to the detection of the oscillation mode signature and the plausible detection of the planetary signal, which, if confirmed with future observations, would be the first detection of phase changes in the visible for a non-transiting planet.
AbstractGamma Dor stars (M = 1.2-2.5 M⊙; spectral type A-F) are very interesting from an asteroseismic point of view. They show gravity modes, which are the only modes that provide information on the deep stellar interior. Observationally they are very challenging targets. Typical pulsation periods are of the order of a day and amplitudes are fairly small (below 0.05 mag; 2 km/s), making it extremely difficult to monitor the periodic variations from the ground. The asteroseismic space missions CoRoT and Kepler are providing uninterrupted time-series from space, with unprecedented accuracy, and hence promise a revolution in the study of gamma Dor stars. I will present results of the seismic analysis of CoRoT and Kepler gamma Dor targets, and the associated ground-based support observations, involving many telescopes at different observatories (including La Palma and Izaña).
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